Group theoretical analysis of double acceptors in a magnetic field: identification of the Si:B^+ ground state

A boron impurity in silicon binding an extra hole is known to have only one bound state at an energy of just below 2 meV. The nature of the Si:B^+ ground state is however not well established. We qualitatively analyze the behavior in a magnetic field of isolated acceptors in a tetrahedral lattice binding two holes using group theory. Applying these results, we analyze recent measurements and conclude that the ground state of B^+ is most compatible with a non-degenerate Gamma_1 state.